1. Field of the Invention
This invention relates to a supervisory control system, and more particularly, to a method and apparatus for an improved supervisory control system.
2. Description of the Prior Art
Supervisory control systems often must operate in an extremely noisy electrical environment. For example, such a system used to monitor and control status monitoring stations for a network of substations and transformers connected to a power plant of a power utility is highly susceptible to the high voltage and electrical noise environment. To cope with such an environment, typically prior art systems have been arranged to repetitively send a signal and detect and compare the repetitively sent signals and send a return signal when the comparison indicates reliable reception. But such a system is not found very reliable when a high level of noise is injected into the system from the power plant substations or transformer or other external sources. Generally the prior art systems are found incapable of providing reliable monitoring and supervisory functions in a noisy environment.
Also it is found that as the number of the monitoring stations increases and as channels allocated for transmission of monitoring, status, supervisory and similar signals get crowded, the prior art supervisory systems are found incapable of expanding their capacity. To increase capacity, the systems require additional communication channels. They are not capable of sharing existing radio channel or using existing voice communication channels. They do not allow easy and inexpensive expansion for additional stations that grow upwards to thousands of stations. Confronted with this situation, some prior art systems resort to manual operation where interrogation of the stations is more generally accomplished by operator assisted manual methods.
In short, none of the prior art systems provides a satisfactory automated supervisory control system that is highly reliable and that can operate in a noisy environment and that can handle large numbers of monitoring stations. For the foregoing and other shortcomings and problems, there has been a long felt need for an improved supervisory control system.